I agree with Mrs. Bradley!!!
Cut off and bag up every leave that is infected with Black spot/rust or fungus.( Every once in a while while cutting off leaves , disinfect your scissors or pruners. I always take a bottle of rubbing alcohol and paper towels with me when I do this and wipe down the blades of scissors especially and completely before moveing on to next rose bush or anything else in the garden
Don't let any leaves lay around on the ground that have a fungus you'd be surprised how quickly one black spot leaf 3 ft away can infect good healthy leaves
Spray with 'rose
Defense spray" ( I use Greenlight products) OR get some neem oil concentrate (* much better economically*) and dilute per direction and after cutting off infected leaves and disposing of them , spray top and under remaining leaves, well before they get full sun for the day, spraying in Early morning is best!, Don't over spray to the point of it Dripping( IT will take too long to dry before the sun gets to it) do this every 7 days for about 3 weeks.. I constantly have this problem here in TX in the spring
when it rains a lot,, or when it's especially humid out,, Every year the same thing
But because I love my roses
I just deal with it!!!